Flutter Fast Forms

Flutter Fast Forms is the only Dart package you need to build Flutter forms fast.

It adds these missing features to the Flutter SDK:

• FastFormControl<T> convenience widgets that wrap Material / Cupertino form controls in a FormField<T> according to the already built-in TextFormField / DropdownButtonFormField
• FastForm widget that wraps the built-in Form widget for providing the current form field values in onChanged callback
• FastFormArray widget that aggregates a flexible number of homogeneous controls in a single FormField<T>
• FastChipsInput widget that converts text input into chips as defined by Material Design
• Conditional form fields
• touched validation state
• Common FormFieldValidator<T> functions

Table of Contents

• Getting Started
• Widget Catalog
• Adaptive Form Fields
• Conditional Form Fields
• Custom Form Fields

Getting Started

1. Add a FastForm to your widget tree:

class MyFormPage extends StatelessWidget {
  MyFormPage({Key? key, required this.title}) : super(key: key);

  final formKey = GlobalKey<FormState>();
  final String title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: SafeArea(
        child: SingleChildScrollView(
          child: FastForm(
            formKey: formKey,
            children: [],
          ),
        ),
      ),
    );
  }
}

2. Add FastFormControl<T> children to the FastForm:

FastForm(
  formKey: formKey,
  children: [
    const FastTextField(
      name: 'field_destination',
      labelText: 'Destination',
      placeholder: 'Where are you going?',
    ),
    FastDateRangePicker(
      name: 'field_check_in_out',
      labelText: 'Check-in - Check-out',
      firstDate: DateTime.now(),
      lastDate: DateTime.now().add(const Duration(days: 365)),
    ),
    const FastCheckbox(
      name: 'field_travel_purpose',
      labelText: 'Travel purpose',
      titleText: 'I am travelling for work',
    ),
  ],
),

3. Wrap the children in a FastFormSection for visual grouping and consistent padding:

FastForm(
  formKey: formKey,
  children: [
    FastFormSection(
      header: const Text('My Form'),
      padding: EdgeInsets.all(16.0),
      children: [
        const FastTextField(
          name: 'field_destination',
          labelText: 'Destination',
          placeholder: 'Where are you going?',
        ),
        // ...
      ],
    ),
  ]
),

Widget Catalog

FastFormControl<T>	field value type	wraps Material widget	wraps Cupertino widget when adaptive: true
FastAutocomplete<O>	String	Autocomplete<O>	no
FastCheckbox	bool	CheckboxListTile	CupertinoCheckbox
FastChoiceChips<T>	Set<T>	ChoiceChip	no
FastCalendar	DateTime	CalendarDatePicker	no
FastChipsInput	List<String>	RawAutocomplete<String> + InputChip	no
FastDatePicker	DateTime	showDatePicker	CupertinoDatePicker
FastDateRangePicker	DateTimeRange	showDateRangePicker	no
FastDropdown<T>	T	DropdownButtonFormField<T>	no
FastRadioGroup<T>	T	RadioListTile<T>	no
FastRangeSlider	RangeValues	RangeSlider	no
FastSegmentedButton<T>	Set<T>	SegmentedButton<T>	no
FastSegmentedControl<T>	T extends Object	no	CupertinoSlidingSegmentedControl<T>
FastSlider	double	Slider.adaptive	CupertinoSlider
FastSwitch	bool	SwitchListTile	CupertinoSwitch
FastTextField	String	TextFormField	CupertinoTextFormFieldRow
FastTimePicker	TimeOfDay	showTimePicker	no use FastDatePicker with CupertinoDatePickerMode.time

Adaptive Form Fields

While some form controls are unique to a certain platform, various others are present in multiple design languages.

By default, Flutter Fast Forms uses Material widgets on any platform.

This behavior is adjustable so that platform-specific Cupertino widgets are automatically rendered on iOS.

Tip

The widget catalog tells you which FastFormControl is adaptive.

📓 Example: Always use Cupertino widgets on iOS in a FastForm.

FastForm(
  formKey: formKey,
  adaptive: true,
  children: [
    const FastSwitch(
      name: 'switch',
      titleText: 'Disable text field',
    ),
    FastTextField(
      name: 'text_field',
      labelText: 'Just some sample text field',
    ),    
  ]
),

Note

• When adaptive is set to true any built-in FormFieldBuilder returns a corresponding Cupertino widget on iOS, if it exists.

📓 Example: Only use the Cupertino widget on iOS for a dedicated FastSwitch.

FastForm(
  formKey: formKey,
  children: [
    const FastSwitch(
      name: 'switch',
      adaptive: true,
      titleText: 'Disable text field',
    ),
  ]
),

Conditional Form Fields

Not all controls in a form are autonomous and act independent of each other.

Occasionally, the state of a form field might be directly related to the state of some other form field as well.

Flutter Fast Forms allows you to define such conditions declaratively.

📓 Example: A FastTextField that is disabled when a FastSwitch is selected.

1. Add the conditions property to the conditional form field and assign an empty Map:

const FastSwitch(
  name: 'switch',
  titleText: 'Disable text field',
),
FastTextField(
  name: 'text_field',
  labelText: 'Just some sample text field',
  conditions: {},
),

2. Choose a suitable FastConditionHandler as Map key and assign a FastConditionList:

const FastSwitch(
  name: 'switch',
  titleText: 'Disable text field when selected',
),
FastTextField(
  name: 'text_field',
  labelText: 'Just some sample text field',
  conditions: {
    FastCondition.disabled: FastConditionList([]),
  },
)

Note

A FastConditionHandler is a function that runs whenever a FastConditionList is checked and determines what happens when the condition is either met or not.

3. Add a FastCondition relating the field to another field:

const FastSwitch(
  name: 'switch',
  titleText: 'Disable text field when selected',
),
FastTextField(
  name: 'text_field',
  labelText: 'Just some sample text field',
  conditions: {
    FastCondition.disabled: FastConditionList([
      FastCondition(
        target: 'switch',
        test: (value, field) => value is bool && value,
      ),
    ]),
  },
),

Note

target is the name of the FastFormField that the form field depends on.

📓 Example: A FastTextField that is enabled when a FastSwitch or a FastCheckbox is selected.

const FastCheckbox(
  name: 'checkbox',
  titleText: 'Enable text field when selected',
),
const FastSwitch(
  name: 'switch',
  titleText: 'Enable text field when selected',
),
FastTextField(
  name: 'text_field',
  enabled: false,
  labelText: 'Just some sample text field',
  conditions: {
    FastCondition.enabled: FastConditionList([
      FastCondition(
        target: 'switch',
        test: (value, field) => value is bool && value,
      ),
      FastCondition(
        target: 'checkbox',
        test: (value, field) => value is bool && value,
      ),
    ]),
  },
),

📓 Example: A FastTextField that is disabled when both a FastSwitch and a FastCheckbox are selected.

const FastCheckbox(
  name: 'checkbox',
  titleText: 'Disable text field when selected',
),
const FastSwitch(
  name: 'switch',
  titleText: 'Disable text field when selected',
),
FastTextField(
  name: 'text_field',
  labelText: 'Just some sample text field',
  conditions: {
    FastCondition.enabled: FastConditionList(
      [
        FastCondition(
          target: 'switch',
          test: (value, field) => value is bool && value,
        ),
        FastCondition(
          target: 'checkbox',
          test: (value, field) => value is bool && value,
        ),
      ],
      match: FastConditionMatch.every,
    ),
  },
),

Note

match specifies how all individual test results in the list are evaluated to determine whether the condition is met.

Custom Form Fields

There are use cases where the widget catalog does not fully satisfy your individual requirements.

As a consequence you have to add non-standard controls to your form.

With Flutter Fast Forms you're free to wrap any custom widget into a form field.

📓 Example: A simple widget that provides a random integer whenever a button is pressed.

1. Create a stateful widget class extending FastFormField<T> with a corresponding FastFormFieldState<T>:

class MyCustomField extends FastFormField<int> {
  const MyCustomField({
    super.builder = myCustomFormFieldBuilder,
    super.key,
    required super.name,
  });

  @override
  MyCustomFieldState createState() => MyCustomFieldState();
}

class MyCustomFieldState extends FastFormFieldState<int> {
  @override
  MyCustomField get widget => super.widget as MyCustomField;
}

Note

• builder and name are required constructor parameters of FastFormField.
• builder is a standard Flutter FormFieldBuilder<T>.

2. Implement the FormFieldBuilder<T> returning your custom widget:

Widget myCustomFormFieldBuilder(FormFieldState<int> field) {
  field as MyCustomFieldState;
  final MyCustomFieldState(:decoration, :didChange, :value) = field;

  return InputDecorator(
    decoration: decoration,
    child: Row(
      children: [
        ElevatedButton(
          child: const Text('Create random number'),
          onPressed: () => didChange(Random().nextInt(1 << 32)),
        ),
        if (value is int)
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 12.0),
            child: Text(value.toString()),
          )
      ],
    ),
  );
}

Note

• Casting field is mandatory to access FastFormField properties and functions.
• Always call field.didChange() to update the value of the form field.

3. Add all super-initializer parameters that the form field should support:

class MyCustomField extends FastFormField<int> {
  const MyCustomField({
    super.builder = myCustomFormFieldBuilder,
    super.decoration,
    super.enabled,
    super.helperText,
    super.initialValue,
    super.key,
    super.labelText,
    required super.name,
    super.onChanged,
    super.onReset,
    super.onSaved,
    super.onTouched,
    super.validator,
  });

  @override
  MyCustomFieldState createState() => MyCustomFieldState();
}

Note

Always make sure that you apply certain super-initializer parameters like decoration or enabled in your builder functions. Otherwise assigning those arguments when invoking the constructor won't have any effect.